Research on pre-calcined temperatures of Ba(Co_1/3Nb_2/3)O₃ microwave dielectric ceramics

Ba(Co_1/3Nb_2/3)O₃ microwave dielectric ceramics were prepared by conventional solid-state method. The effects of pre-calcined temperatures on the phase composition, microstructure, sintering property and microwave dielectric property were studied. The results showed that the main crystal phase of the ceramics under the different pre-calcined temperatures was Ba₃CoNb₂O₉ with complex perovskite structure, but small amount of Ba₃Nb₅O₁₅ appeared when the pre-calcined temperature was 900°C and 1000°C. The optimal microwave dielectric properties were obtained with ε_r of 31.8, Q×f of 60164 GHz and τ_f of -15 × 10^-6/°C when the pre-calcined temperature was 1100°C and the sintering temperature was 1380°C for 4 h. The optimized pre-calcined temperature prevented the formation of the second phase, which improved the compactness of the material and made the atoms of B site in the main crystal phase be well ordered and further reduced dielectric loss.